Solid propellant compositions and method of modifying propellant burning rate using ferrocene derivatives



United States Patent O 3,447,981 SOLID PROPELLANT COMPOSITIONS AND METHOD OF MODIFYING PROPELLANT BURNING RATE USING FERROCENE DERIVATIVES David C. Sayles, Huntsville, Ala., assiguor to the Umted States of America as represented by the Secretary of the Army No Drawing. Filed Nov. 1, 1962, Ser. No. 235,601 Int. Cl. C06b 11/00 U.S. Cl. 149-19 11 Claims The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates to an improvement in solid propellants and more specifically to bis(cyclopentadienyl)iron derivatives containing reactive functional groups which act as burning rate accelerators in solid propellants.

The use of bis(cyclopentadienyl)iron in solid propellant compositions as a burning rate accelerator is well known in the art. However, this compound has inherent shortcomings which limit its usefulness. The first of these faults is that the bis(cyclopentadienyl)iron does not react with any of the ingredients in the propellant composition thereby lending itself to easy loss from the composition. This loss may occur during compounding by entrainment in vaporizing liquids or it may occur by sublimation after the propellant has undergone polymerization. Another fault of bis(cyclopentadienyl) iron is its poor compatibility with other ingredients in the propellant composition.

This invention employs bis(cyclopentadienyl) iron derivatives containing reactive functional groups to overcome these aforementioned shortcomings. These compounds can be used in solid propellant fuels to replace bis(cyclopentadienyl)iron which is currently utilized as a burning rate modifier. The bis(cyclopentadienyl) iron derivatives disclosed in this invention have many advantages over the previously used bis(cyclopentadienyl)iron. In addition to being as effective as a burning rate accelerator as bis(cyclopentadienyl)iron, these additives react with the cross linking agents of the propellant composition during curing to form an integral segment of the polymeric binder and result in a propellant composition having more uniform and more reproducible burning rate characteristics. Unlike bis(cyclopentadienyl)iron, these compounds are not lost from the propellant composition during the compounding step. Also, they are not lost by sublimation after the propellant has undergone polymerization. Finally, these compounds are more compatible with the other ingredients in propellant compositions than is bis(cyclopentadienyl)iron.

Therefore it is an object of this invention to provide burning-rate modifiers which form an integral segment of the polymer binder and result in a propellant composition having more uniform and reproducible burning rate characteristics.

It is a further object of this invention to provide burning rate modifiers which are not lost from the propellant composition by mechanical entrainment or sublimation. One other object of the instant invention is to provide burning rate modifiers which, when used in propellant compositions, are more compatible with the other ingredients of the propellant composition than bis(cyclopentadienyl)iron.

Another object of the instant invention is to provide an improved method of modifying the burning rate of solid propellant compositions wherein bis(cyclopentadienyl) iron has previously been employed.

These and other objects will become apparent to one skilled in the art upon reading the more detailed discussion presented hereinafter.

3,447,981 Patented June 3, 1969 The objects of this invention are accomplished by the substitution of a compound selected from the group consisting of cyclopentadienyl-[2(l-hydroxyethyl)-cyclopentadienyl]iron, 2 carboxycyclopentadienyl(cyclopen'tadienyl)iron, and 2 isocyanatocyclopentadienyl(cyclopentadienyl)iron for bis(cyclopentadienyl)iron when it is used in solid propellant compositions as a burning rate accelerator. These derivatives are employed in the propellant composition in quantities of 1% to 2% by weight.

The bis(cyclopentadienylfiron derivatives used in the instant invention are known in the art and may be obtained according to prior art techniques.

Other rnetallocenes, such as ruthenocene and osmocene, will undergo a similar series of reactions and function similarly as propellant burning rate modifiers.

The invention is further illustrated by the following examples of suitable propellant compositions. In the examples listed the bis(cyclopentadienyl)iron derivative reacts with the cross linking agent, such as tris(me'thylaziradinyl)phosphinic oxide since it has three functional groups. However, this cross linking agent can be replaced by any other tri-functional agent. Furthermore, it is not necessary that a tri-functional cross linking agent be present since the bis(cyclopentadienyl)iron derivative can react with any functional group in the propellant compositiqn thereby becoming an integral part of the composition. It is to be understood that these examples are for purpose of exemplification and that the invention is not limited thereto.

Example I Formulation: Wt. percent Polybutadiene-acrylic acid prepolymer 15 Tris(methylaziradinyl)phosphinic oxide 2.5 Ammonium perchlorate 66.5 Aluminum powder 15.0 Cyclopentadienyl [2 (1 hydroxyethyD-cyclopentadienyl]iron The formulation is mixed in any manner to insure thorough mingling of the ingredients and cured at The formulation is mixed and cured as in Example I.

As many possible embodiments can be made of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and that the invenion is limited only by the appended claims.

I claim:

1. In the method of accelerating the burning rate of solid propellant compositions with bis(cyclopentadienyl) iron as the burning rate accelerator, the improvement in said method which comprises the substitution in said propellant composition of a compound selected from the group consisting of cyclopentadienyl-[2-(1-hydroxyethyl)- cyclopentadienyl]iron, 2 carboxycyclopentadienyl(cyclopentadienyl)iron, and 2 isocyanatocyclopentadienyl(cyclopentadienyl)iron for said bis(cyclopentadieny1)iron.

2. The method of claim 1 wherein said compound is cyclopentadienyl [2 (1 hydroxyethyl) cyclopentadienyl]iron.

3. The method of claim 1 wherein said compound is 2- carboxycyclopentadienyl (cyclopentadienyl iron.

4. The mehtod of claim 1 wherein said compound is 2-isocyanatocyclopentadienyl (cyclopentadienyl iron.

5. In solid propellant compositions employing bis(cyclopentadienyl)iron as the burning rate accelerator, the improvement in these compositions which comprises the substitution of a compound selected from the group consisting of cyclopentadienyl [2-( l-hydroxyethyl)-cyclopentadienyl1iron, 2 carboxycyclopentadienyl(cyclopentadienyl)iron, 2 isocyanatocyclopentadienyl(cyclopentadienyl)iron for said bis(cyclopentadienyl)iron.

6. The composition of claim 5 wherein said compound is cyclopentadienyl [2 (1 hydroxyethyl) cyclopentadienyl] iron.

7. The composition of claim 5 wherein said compound is 2-carboxycyclopentadienyl(cyclopentadienyl)iron.

8. The composition of claim 5 wherein said compound is 2-isocyanatocyclopentadienyl(cyclopentadienyl)iron.

9. A solid propellant composition consisting essentially of a cured intimate mixture of about 15 weight percent polybutadiene-acrylic acid copolymer, about 2.5 weight 4 percent tris(methylaziradinyl) phosphinic oxide, about 66.5 weight percent ammonium perchlorate, about 15 weight percent aluminum powder, and about 1 weight percent cyclopentadienyl [2 (1 hydroxyethyl) cyclopentadienyl] iron.

10. A solid propellant composition consisting essentially of a cured intimate mixture of about 62 weight percent ammonium perchlorate, about 20 weight percent aluminum powder, about 14 weight percent polyurethane polymer, about 2 weight percent hydroxyl-terminated polypropylene ether, about 0.01 weight percent triethanolamine, and about 2 weight percent Z-isocyanatocyclopentadienyl (cyclopentadienyl) iron.

11. A solid propellant composition consisting essentially of a cured intimate mixture of about 15 weight percent polybutadiene-acrylic acid copolymer, about 2.5 weight percent tris(methylaziradinyl) phosphinic oxide, about 66.5 weight percent ammonium perchlorate, about 15 weight percent aluminum powder, and about 1 weight percent 2-carboxycyclopentadienyl (cyclopentadienyl) iron.

References Cited UNITED STATES PATENTS 3,002,830 10/1961 Barr 149-19 3,038,299 6/ 1962 Pedersen 149-74 X BENJAMIN R. PADGETT, Primary Examiner.

US. Cl. X.R. 149-109, 44 

5. IN SOLID PROPELLANT COMPOSITIONS EMPLOYING BIS(CYCLOPENTADIENYL) IRON AS THE BURNING RATE ACCELERATOR, THE IMPROVEMENT IN THESE COMPOSITIONS WHICH COMPRISES THE SUBSTITUTION OF A COMPOUND SELECTED FROM THE GROUP CONSISING OF CYCLOPENTADIENYL(2-(1-HYDROXYETHYL)-CYCLOPENTADIENYL)IRON, 2-CARBOXYCLOPENTADIENYL(CYCLOPENTADIENYL)IRON, 2-ISOCYANATOCYCLOENTADIENYL(CYCLOPENTADIENYL)IRON FOR SAID BIS(CYCLOPENTADIENYL)IRON. 